PREVIOUSLY ON LOST

If only Sayid had gotten on the original flight that CIA had offered him, then he wouldn’t have been on Flight 815, his plane would never have crashed and he would have probably been reunited with Nadia.

When Sayid asks Locke to take him to the plane you can sense that he could very well intended to kill him, but when they get to the plane you can tell that Sayid starts to believe Locke’s story. Then Locke’s goes and springs the revelation that it was he who ‘attacked’ Sayid while he was trying to triangulate the distress signal, and all that trust goes flying out the window.